1. Field of the Invention
This invention relates to the field of seals incorporating intumescent material, which expand under thermal stress, to seal gaps in doorways, windows and the like to prevent passage or penetration of smoke, noxious fumes and the like. More particularly, this invention relates to an improved fire seal wherein the intumescent material may be selectively activated responsive to remotely sensed alarm conditions, for example, wherein a fire detected in any room of a structure may result in every single window and doorway in the structure being sealed.
2. Prior Art
Intumescent materials are those which swell or expand upon continued exposure to fire or heat. Typical intumescent materials comprise a fire retardant composition having an intumescent component, such as hydrated alkali metal silicate in granular form, an organic binder component, organic char-forming components such as a phenolic resin, and fillers. An example of such a material sold in sheet form is "Fire Barrier Sheet FS-195" available from the 3M Company. These sheets remain in their flexible, unexpanded state under normal conditions, but when subjected to temperatures on the order of 110.degree. C. and higher, readily intumesce up to ten times their original volume to form a rigid char and thereby seal a gap against the passage of fire, heat, smoke, vapors and water. Such a char is strong, highly refractory, and is not easily blown out of a gap when subjected to water hose pressure. Other intumescent materials include "Palusol" sold by BASAF and "Expantrol" sold by the 3M Company. In will be appreciated that the particular form of intumescent material utilized in this invention does not form a part of the invention in and of itself. Of course, certain types may prove most beneficial in different circumstances. Accordingly, the chemical composition and characteristics of such intumescent materials need not be considered herein in detail.
The prior art has recognized that intumescent material may be incorporated into weather stripping and other kinds of seals normally used for doorways and windows. A reservoir of intumescent material is provided along the weather strip or seal, and in the event of fire-like ambient conditions adjacent the doorways or windows, the intumescent material will expand out of the reservoir and, theoretically, seal the gap against penetration of smoke, noxious fumes and the like. The following patent references are typical of sealing strips known in the art which incorporate intumescent material for fire-sealing purposes.
United Kingdom published Application No. GB 2 106 972 A--Dixon discloses a retrofit door seal incorporating intumescent material in a pocket separate from the weather seal. The intumescent material is not held, formed or mounted integrally with the conventional door seal portion of the seal. The intumescent material responds only to ambient conditions, and there is no suggestion that it can or should be remotely activated.
United Kingdom published Patent Application No. GB 2 092 214 A--Schroders discloses a door seal wherein a reservoir of intumescent material is integral with the structure forming the conventional portion of the door seal, but as in Dixon above, there is no suggestion that the intumescent material can or should be remotely activated.
U.S. Pat. No. 4,364,210--Fleming, et al. discloses a fire and smoke resistant construction for sealing a penetration of a passageway through a fire-resistant wall, floor, partition or the like. The construction includes an insert of intumescent material mounted at one end of the penetration and adapted to expand and fill the penetration when heated to its activation temperature. In accordance with an alternative embodiment, an end cap formed of plastic laminated intumescent material is provided, through which wires, cables or the like may be passed. The end cap seals the penetration at low ambient temperatures. There is no suggestion that the intumescent material can or should be remotely activated.
There is another class of products in which intentional activation of a thermally sensitive material is effected, although none are known to be in the context of fire seals. The following references are typical of manipulating thermoplastic materials.
U.S. Pat. No. 3,936,661--Furuishi, et al. discloses an electrothermally deformable leveling pad, including one or more plate members made of thermoplastic material, and at least one electric heater adjacent one surface of the plate member. The structure is employed for leveling heavy structural elements, such as railroad rails. Upon heating, the thermoplastic layer softens slightly and becomes compressible under load. When the heating element is turned off, the material hardens and becomes stable at a thickness which is less than its original thickness. There is no suggestion that the electrothermal activation system used by Furuishi, et al. could or should be used for remotely activating intumescent material in weather stripping, fire seals and the like.
U.S. Pat. No. 4,115,609--Denman discloses a sealing element which is useful, inter alia, in mounting automobile windshields. The structure is similar in theory to that of Furuishi, et al., in that it includes an elongated body of a butyl or ethylene-propylene rubber composition, rather than a body intumescent material. Denman does teach that a heating element can be embedded in the thermoplastic material, for softening the material. However, the rubber material does not expand upon heating, but rather, changes from a resilient state to a plastically deformable, but otherwise stable state. Upon cooling, the strip retains the shape into which it was forced during heating by the load presented by those members joined by the strip. There is no suggestion that a heating element can or should be embedded in an intumescent material forming part of a weather strip or fire seal, to enable remote activation of the intumescent material.
Finally, U.S. Pat. No. 4,323,607--Nishimura, et al. discloses a heat-shrinkable cover for sealing the joint between two pipes or the like. The heat-shrinkable cover has heating wires or cables embedded therein, the wires being oriented in a direction so as not to interfere with shrinkage of the cover. There is no suggestion that such a heating system can or should be employed with intumescent material forming part of a weather strip or fire seal.
Although it is apparently known in the art to form weather strips or fire seals with reservoirs of intumescent material, and although it is known to use electrothermal systems for heating and shaping thermoplastic materials, it has apparently not occurred to those skilled in either of these disparate arts to provide a fire seal having a reservoir of intumescent material, together with means for remotely activating the intumescent material responsive to detection of alarm conditions remote from the fire seal. Those skilled in the respective arts have apparently also failed to appreciate that such remotely activatable fire seals can be incorporated into comprehensive fire or gas protection systems. This invention is primarily directed to remotely activatable fire and gas seals and fire and gas protection systems incorporating such remotely activatable seals.
Other references which may be of interest, insofar as they relate generally to fire seals and useful compositions of intumescent materials, but which nevertheless fail to even suggest the invention taught herein, are U.S. Pats. Nos. 4,045,930--Dixon; 4,320,611--Freeman; 4,467,577--Licht; and, 4,468,043--Brazel.
As may well be appreciated, as useful as known fire seals may be in preventing passage or penetration of smoke and noxious fumes through doorways and windows, it is often too late by the time the gaps in such structures are sealed. It is important to realize that closing gaps cannot only prevent damage or injury, but in many instances, can reduce the flow of oxygen to a fire, and so retard expansion of the fire from its starting point. The ambient temperatures necessary to activate typical intumescent materials are such that one immediately on the other side of a doorway, for example, in which the intumescent material is activated, is already in significant danger from smoke and noxious fumes. It is also quite conceivable, for example, that one might wish to delay activation of intumescent seals until after a building or a portion of a building has been evacuated, in order that subsequent opening and closing of the doorways will not destroy the fire seals. Fire, smoke and gas control systems according to this invention, incorporating seals having remotely activatable intumescent reservoirs, are easily incorporated into automatically and manually controlled systems, as well as hybrids, and particularly computer controlled systems. The advantages of remotely activatable expandable seals have apparently escaped those skilled in the art. The invention taught herein indeed fills a significant gap in available fire, smoke and gas control systems.